Absolom!
There have been several cities that are detailed in Campaign Guides. I guess it depends on the nature of the city you want to play in.
Absalom is the largest city in the Inner Sea Region, and is the de facto cultural capital. It is described in the Guide to Absalom.
Korvosa is a moderately-sized city-state in the frontier land of Varisia. It's a former colony of the Empire of Cheliax, and still has close ties. It's also the setting of the "Curse of the Crimson Throne" Adventure Path. It is described in the excellent Guide to Korvosa.
Katapesh is a middle-eastern themed city in the desert lands far to the east. It is a city of merchants where anyone can purchase anything. Its population rivals Absalom's. It is detailed in Dark Markets: A Guide to Katapesh.
Kaer Maga is a small city in the edge of civilization in Varisia, where everyone is welcome... as long as you stay out of other people's business. It's kind of got a "Mos Eisley Spaceport" vibe. The excellent guide City of Strangers details this fascinating city.
I've set my campaign near the Varisian port city of Magnimar, an open-yet-corrupt city that's barely held together by a loose coalition of squabbling interests. It's detailed in Magnimar: City of Monuments.
The Campaign Setting book Cities of Golarion details six additional cities, although in less fine detail than the previous guides. This book has information on:
* Cassomir, decaying capital of the once-proud Taldor Empire.
* Corentyn, port city of the devil-haunted Empire of Cheliax.
* Ilizmagorti, pirate city and home of the Red Mantis Assassin's Guild.
* Nisroch, shadowy capital of Nidal and seat of the church of the Midnight Lord Zon-Kuthon.
* Vigil, bastion of paladins that watches over the tomb of the defeated lich-king the Whispering Tyrant.
* Whitethrone, capital of the witch-queens of frozen land of Irrisen.
I own the Magnimar, Kaer Maga, and Cities of Golarion books; and I've read the Guide to Korvosa. Of these, my favories are Magnimar and Kaer Maga.
Magnimar is probably the most "normal" of the cities, although it's still rife with intrigue and baked-in plot hooks. The Magnimar: City of Monuments is one of my favorite gaming resource guides, period.
While Nisroch is the largest and most accessible city in Nidal, the capital is actually Pangolais.
And Cassomir is actually a (relatively) thriving port and shipbuilding city. The capital of Taldor is Oppara.
You're both right: I wrote that from memory. My campaign is pretty much exclusively in Varisia, so I'm not nearly as familiar with other regions.
To the above, one should probably add that the Council of Thieves adventure path is set entirely in the Chelaxian city of Westcrown. In addition to the information given in the actual adventures, there's a support article in Pathfinder #25 and the (free to download) Council of Thieves Player's Guide.
And the Players Guide to Second Darkness had an extensive gazetteer for the anarcho-libertarian city of Riddleport.